1. Field of the Invention
The present invention relates to a heat resistant rubber laminate composed of a rubber base layer and a fluorine-containing heat resistant top cover.
2. Description of the Prior Art
Heretofore, as the general heat resistant rubbers, chloroprene (CR), butyl rubber (IIR), halogenated butyl rubber, ethylene-propylene-nonconjugated terpolymeric rubber (EPDM) and ethylene-propylene copolymeric rubber (EPR) have been well known and these rubbers have been used for producing industrial rubber products in many cases, because these rubbers are excellent in the processability and have a high adhesion to the other materials and are relatively inexpensive. However, when these rubbers are used as a top cover of the heat resistant conveyor belt, the heat resistance is not necessarily satisfied and these rubbers cannot endure use for a long time under a high temperature condition.
As an embodiment, a heat resistant conveyor belt provided with the top cover consisting mainly of EPDM has been proposed but when this conveyor belt is used at a temperature higher than 150.degree. C., the top cover is aged and hardening and cracks are caused and growth of cut is noticeable, so that this conveyor belt cannot endure use for a long time.
As the specific heat resistant rubbers, there are acrylic rubber, epichlorohydrin rubber (CHR), epichlorohydrinethylene oxide copolymeric rubber (CHC), silicone rubber, fluorine rubber and the like and among these rubbers, silicone rubber and fluorine rubber have a heat resistance up to about 150.degree.-200.degree. C., so that these rubbers have been expected to be used as the material for rubber articles for a super high temperature. However, these specific heat resistant rubbers are not only very expensive, but also there is a problem in the technic for adhering to other materials, so that the use is limited to a very narrow field.
Accordingly, the heat resistant rubber articles are usually produced from the above described general heat resistant rubbers, so that the use scope is limited within a lower temperature range as compared with the above described specific heat resistant rubbers.